This invention concerns a key transpose process of an electronic musical instrument, and particularly an electronic musical instrument, wherein the state of a key transpose switch and depressed key signals of a key board switch are analyzed to obtain key transpose data, so that the instrument may readily transpose a key.
Generally, the key transpose is accomplished by raising or lowering the key, at which a music is played, by a semitone (half tone). A conventional electronic musical instrument having the key transpose function, as shown in FIG. 1, includes a key transpose switching unit 100 for generating a key transpose signal, and microcomputer 110 for processing the depressed key signals of key board switch 108 according to the key transpose signal.
The key transpose switching unit 100 includes key transpose switch 104, up-key transpose switch 102 and down-key transpose switch 106, in which the up and down-key transpose switches 102, 106 should be selectively depressed a desired number of times to generate a control signal for controlling the microcomputer 110 to produce the key transpose data to the depressed key signals of the key board switch 108. The key transpose data is applied to a sound generator 112 to produce key-transposed sound delivered to a speaker 120 through a digital to analog converter (D/A converter) 114, amplifier 116 and low pass filter 118.
In such a conventional electronic musical instrument, there is an inconvenience in that the player of the instrument must count the number of half tones included between the presently played key and the key to be transposed, so that the player may selectively operate the up and down-key transpose switches 102 and 106 according to the number of the half tone, thereby accomplishing the key transpose.